Physicians make use of catheters today in medical procedures to gain access into interior regions of the body to ablate targeted tissue areas. It is important for the physician to be able to precisely locate the catheter and control its emission of energy within the body during tissue ablation procedures.
The need for precise control over the catheter is especially critical during procedures that ablate myocardial tissue from within the heart. These procedures, called electrophysiological therapy, are used to treat cardiac rhythm disturbances.
During these procedures, a physician steers a catheter through a main vein or artery into the interior region of the heart that is to be treated. The physician then further manipulates a steering mechanism to place the electrode carried on the distal tip of the catheter into direct contact with the endocardial tissue. The physician directs energy from the electrode through myocardial tissue either to an indifferent electrode (in a uni-polar electrode arrangement) or to an adjacent electrode (in a bi-polar electrode arrangement) to ablate the tissue and form a lesion.
Physicians examine the propagation of electrical impulses in heart tissue to locate aberrant conductive pathways and to identify foci, which are ablated. The techniques used to analyze these pathways and locate foci are commonly called "mapping."
Conventional cardiac tissue mapping techniques use multiple electrodes positioned in contact with epicardial heart tissue to obtain multiple electrograms. These conventional mapping techniques require invasive open heart surgical techniques to position the electrodes on the epicardial surface of the heart.
An alternative technique of introducing multiple electrode arrays into the heart through vein or arterial accesses to map myocardial tissue is known. Compared to conventional, open heart mapping techniques, endocardial mapping techniques, being comparatively non-invasive, hold great promise. Multiple electrogram signals obtained from within the heart can be externally processed to detect local electrical events and identify likely foci.
To achieve consistent, reliable foci identification rates, all electrodes in a multiple electrode array should be in intimate, electrical contact with heart tissue. With invasive, open heart techniques, multiple electrode contact on exposed epicardial surfaces can be visually confirmed directly by the physician. However, with comparatively non-invasive endocardial mapping techniques, confirming multiple electrode contact within the beating heart can be problematic.
There is the need to provide simple, yet reliable ways of assuring that the electrodes of an endocardial multiple electrode structure are in intimate, electrical contact with tissue within the heart.